beta-Endorphin. Circular dichroism of synthetic human analogs with various chain lengths in methanol solutions.

The alpha-helix content of human beta-endorphin (beta h-EP) has been determined by circular dichroism (CD) in solutions ranging from 0 to 95% methanol in water. In addition, the CD spectra of beta h-EP-(1-30),-(1-29),-(1-28),-(1-27),-(1-26),-(1-21) and -(1-15) have been examined in 90% methanol, and their alpha-helix contents estimated using parameters determined for this solvent. Addition of methanol to beta h-EP solutions brings about a noncooperative formation of alpha-helix. An attempt to correlate secondary structure in methanol with biological and immunological activities showed limited direct correspondence, but may indicate the involvement of the tertiary interactions.